The invention is related to a method of processing a ceramic layer. The invention is also related to devices made therefrom.
Thermal spray processes, such as air plasma spray, have been extensively used to fabricate ceramic layers. These processes have the potential to provide large-area ceramic layers at reasonably low manufacturing costs. Therefore, air plasma spray could be used in the commercial manufacture of ceramic electrolytes for use in solid oxide fuel cells. However, air-plasma-sprayed coatings typically contain both pores and microcracks, which in the case of a ceramic electrolyte may provide leak paths for the fuel and air.
Microcracks are typically formed at interlamellar splat boundaries during deposition, or are formed through the thickness of the coating, due to large thermal expansion strains caused during processing and operation. Such defects may limit the open cell voltage and fuel utilization. Efforts are being made to increase the density of deposited ceramic electrolyte layers, and to minimize their defects, but most of them involve high processing temperatures. When the ceramic electrolyte layers are disposed on metals at high processing temperatures, high oxygen partial pressures may lead to unwanted oxidation. Oxidation and thermal cycling may also cause serious problems, including delamination of the electrolyte. Therefore, there is a continuous need to improve the performance of ceramic electrolytes, and a need for versatile methods to fabricate ceramic electrolytes having substantially reduced permeability.